Propeller design



July 9, 1963 L. MEYERHOFF 3,096,930

PROPELLER DESIGN Filed June 26, 1961 INVENTOR. 160M490 Maya HOFF BY z/ United States Patent 3,096,930 PROPELLER DESIGN Leonard Meyerhoif, Brooklyn, N.Y., assignor to Leonard Meyerhoit and Stanley A. Meyerhoif, doing business as Eastern Research Group, a partnership Filed June 26, 1961, Ser. No. 119,443 6 Claims. (Cl. 23012i)) This invention relates to a propeller design which substantially eliminates problems associated with clearance between the peripheral edge of a rotating propeller blade and the housing therefor.

In the design of enclosed propellers, such as for example a pump impeller or a marine propeller contained within a duct or housing, the clearance between the peripheral edge of the propeller blade and the housing must be designed on a compromise basis.

Obviously, a minimum of clearance is necessary in order to prevent binding or rubbing between the peripheral edge of the blade and the housing. In addition to this minimum clearance, it is generally necessary to add additional clearance to compensate for the usual tolerances in production of the various parts which are associated to form the unit.

The relatively large clearances that are thus required are disadvantageous for several reasons. First, there is a loss of efliciency due to the fact that the fluid through which the propeller is rotating is enabled to flow from the downstream side of the propeller to the upstream side through the clearance space. An additional dis-advantage which becomes of great importance where detection is to be avoid involves the noise which results from the aforementioned backflow. This noise results directly from the gap vortex cavitation arising from the large clearance.

Accordingly, it is an object of this invention to provide an enclosed propeller blade design which will provide the necessary clearance required by factors such as manufacturing tolerances, while substantially eliminating decreased efliciency and gap vortex cavitation.

It is an additional object of this invention to provide a propeller blade for use in ducts and housings which is provided with a peripheral slotted area thereby creating a fluid radial extension of the blade which effectively seals the clearance area and thus eliminates the disadvantages stemming from backflow.

Briefly stated, the present invention relates to an enclosed propeller blade design in which a conduit is formed within the peripheral area of the blade, the conduit being provided with an opening in the leading edge of the blade. The conduit is connected to the peripheral edge of the propeller blade by an elongated slot extending substantially along the entire length of the conduit. Thus, rotation of the propeller causes induction of fluid into the conduit. The induced fluid in turn flows out of the propeller blade in a radial direction through the elongated slot. In effect, the fluid flowing out of the elongated slot forms a curtain which acts as a fluid extension of the propeller blade and substantially eliminates backflow.

The invention may be more readily understood when described in conjunction with the drawings in which:

FIG. 1 is an elevational view, partly in section, of one embodiment of the enclosed propeller blade design of this invention.

FIG. 2 is a developed plan view, partly broken away, of the propeller blade of FIG. 1 taken along line 22 therein; and

FIG. 3 is a sectional view taken as shown in FIG. 2.

With respect now more particularly to the drawings, FIG. 1 is a front elevational view of one embodiment of the enclosed propeller blade design of this invention. Shown in FIG. 1 is propeller blade attached to hub 11 and rotatable about point 12 in the direction shown by the arrow. Also shown in FIG. 1 is housing wall 13. The essence of this invention involves the conduit 14 which is shown intersecting the leading edge 15 at entrance 16 of blade 10.

An elogated slot 17, shown in section in FIG. 3, extends along the entire length of conduit 14.

As blade 10 rotates, fluid is induced into entrance 16. This fluid flows through conduit 14 and is directed in a radial direction through slot 17 so that a curtain of fluid impinges against housing wall 13. By reason of the relatively high pressures developed at the leading edge 15 of the enclosed propeller blade 10, the force with which the fluid is expelled through slot 17 is considerable. Accordingly, the curtain of fluid which serves as an extension of blade 10, prevents backflow. Further, when the fluid is compressible, the density of this curtain varies in proportion to the pressure developed at the leading edge 15 of the propeller blade 10 and this pressure varies in proportion to the speed of the blade so that the faster the blade rotates the denser the curtain and vice versa. This is an important automatic regulating feature. With increased propeller blade speed there is also increased pressure diiferential across the propeller and therefore an increase in backflow pressure which is proportionally countered by the related increase in density of the curtain. Thus, for air utilizing devices, with increase or decrease in blade speed the backflow pressure and countering curtain density tend to increase and decrease automatically and in proportion to assure prevention of backflow at varying blade speeds.

Although the embodiment shown in FIGS. 1, 2 and 3 has been described in terms of a propeller, it is to be appreciated that the invention is applicable to any device in which a propeller blade is rotated for the purpose of causing a flow of fluid. Thus, centrifugal pumps are amenable to design in accordance with the present invention, as well as other types of fluid flow devices in which a blade is rotated within an enclosure.

With respect once again to FIG. 1, conduit 14 is shown to be tapered. This is the preferred form and is employed since the magnitude of flow within the conduit 14 diminishes uniformly from the entrance 16 downstream. Accordingly, to insure a uniform flow through elongated slot 17, conduit 14 is tapered to diminish the cross-sectional areas thereby maintaining fluid pressure along the slot while compensating for the loss of fluid.

The shape or geometric design of entrance 16 is not critical, and may be chosen so that a decelerating elfect on the induced fluid is produced thereby giving rise to an increase in pressure. Conversely if it is desired, the form of entrance 16 may be made to have an accelerating effect on the induced fluid with an accompanying decrease in pressure.

Thus, the presentinvention provides a simple solution to the problems caused by the necessity for having clearance between the peripheral edge of a propeller blade and the housing. Enclosed propeller blades may be designed in accordance with this invention with suflicient clearance to allow for all of the standard manufacturing tolerances without being burdened by the disadvantages arising therefrom.

What has been described above is one embodiment of an enclosed propeller blade design of this invention which provides radial fluid flow which acts as an extension of the propeller blade. Thus, the disadvantages arising from backflow in the clearance between the conventional propeller blade and housing are obviated.

The present invention also applies to flow devices in which a propeller is driven by the incoming flow, e.g., turbine. In such situations, the static pressure of the fluid flowing is diminished by passage through the device. Hence the gap flow at the periphery of the propeller or blade will be in a direction from upstream to downstream, the reverse of the situations described in the examples above. Accordingly, the direction of flow from the conduit is made opposite to that of the illustrative embodiment.

Although the examples described employ a slot for the issuance of a curtain of water, it is to be understood that advantages of this invention may be obtained if the water flow which forms the curtain issues from a single point on the periphery of the propeller. For example, gap flow is known to curl into a rope-like gap vortex which can be destroyed by the aforementioned single point issuance.

More than one curtain of fluid may be employed in accordance with this invention to obtain increased advantages. Thus, the use of a double curtain would proportionately decrease the gap flow.

It is to be understood that the embodiment described above is intended merely as illustrative of the present invention and that variations may be made therein by one skilled in the art without departing from the spirit and scope of .this invention.

What is claimed is:

1. An enclosed propeller blade assembly comprising a blade mounted to rotate about an axis, a housing for said blade, said housing being circular in shape and concentric with the cylindrical surface described by the periphery of said blade leaving a determinate clearance between its inner surface and said cylindrical surface, the said blade having a peripheral portion and a leading edge and being provided with a conduit configured substantially similar to and located adjacent said peripheral portion, said conduit intersecting the leading edge of said blade and having an, opening formed at such intersection, an elongated slot located in the peripheral portion of said blade and being longitudinally coterminous with said conduit, said slot longitudinally intersecting both the conduit and the periphery of said blade, whereby rotation of said propeller blade causes fluid to enter said opening, the fluid so entering then flowing through said conduit and escaping from said conduit through said slot thereby forming a curtain of fluid between the periphery of said blade and said housing.

,2. In the assembly of a rotatable propellerenclosed within a housing, a propeller comprising a blade having a peripheral portion and a leading edge, a conduit configured substantially similar to and located adjacent the peripheral portion of said blade, said conduit intersecting the leading edge of said blade and having an opening formed at such intersection, an elongated slot located in the peripheral portion of said blade and being longitudinally coterminous with said conduit, said slot longitudinally intersecting both the conduit and the periphery of said blade, whereby rotation of said propeller blade causes fluid to enter said opening, the fluid so entering then flowing through said conduit and escaping from said conduit through said slot thereby forming a curtain of fluid between the periphery of said blade and said housing.

3. The combination comprising a propeller having at least one blade having a peripheral portion and a leading edge mounted thereon so that rotation of said propeller causes said blade to provide a flow of fluid parallel to the axis of rotation, a conduit configured substantially similar to and located adjacent the peripheral portion of said blade, said conduit intersecting the leading edge of said blade and having'an opening formed at such intersection, a housing surrounding said propeller, an annularly shaped space between said housing and the cylindrical surface described by the periphery of said blade when said propeller is rotated, an elongated slot located in the peripheral portion of said blade and being longitudinally coterminous with said conduit, said slot longitudinally intersecting both the conduit and the periphery of said blade, whereby rotation of said propeller blade causes fluid to enter said opening, the fluid so entering then flowing through said conduit and escaping from said conduit through said slot thereby forming a curtain of fluid between the periphery of said blade and said housing.

4. In the assembly of a rotatable propeller enclosed within a housing, a propeller comprising a blade having a peripheral portion and a leading edge and being mounted so that rotation of said propeller causes said blade to provide a flow of fluid parallel to the axis of rotation, the periphery of said blade being spaced from the housing by an annularly shaped clearance, a conduit configured substantially similar to and located adjacent the peripheral portion of said blade, said conduit intersecting the leading edge of said blade and having an opening formed at such intersection, an elongated slot located in the peripheral portion of said blade and being longitudinally coterminous with said conduit, said slot longitudinally intersecting both the conduit and the periphery of said blade, whereby rotation of said propeller blade causes fluid to enter said opening, the fluid so entering then flowing through said conduit and escaping from said conduit through said slot thereby forming a curtain of fluid between the periphery of said blade and said housing. 5. In an assembly of a rotatable propeller enclosed within a housing, a propeller comprising a blade having a peripheral portion and a leading edge and being mounted so that rotation of said propeller causes said blade to provide a flow of fluid parallel to the axis of rotation, said blade having a curved periphery substantially concentric With the said axis of rotation, a conduit located adjacent the peripheral portion of said blade, said conduit having a curved longitudinal axis which substantially follows the curvature of the periphery of said blade, said conduit intersecting the leading edge of said blade and having an opening formed at such interesection, an elongated slot located in the peripheral portion of said blade and being longitudinally coterminous with said conduit, said slot longitudinally intersecting both the conduit and the periphery of said blade, whereby rotation of said propeller blade causes fluid to enter said opening, the fluid so entering then flowing through said conduit and escaping from said conduit through said slot thereby forming a curtain of fluid between the periphery of said blade and said housing.

6. In the assembly of a rotatable propeller enclosed within a housing, a propeller comprising a blade having a peripheral portion and a leading edge and being mounted so that rotation of said propeller causes said blade to provide a flow of fluid parallel to the axis of rotation, said blade having -a curved periphery substantially concentric with the said axis of rotation, a tapered conduit configured substantially similar to and located adjacent the peripheral portion of said blade, said conduit having a larger cross-sectional area adjacent the leading edge of said blade, said conduit interesecting the leading edge of said blade and having an opening formed at such intersection, an elongated slot located in the petripheral portion of said blade and being longitudinally coterminous with said conduit, said slot longitudinally interesecting both the conduit and the periphery of said blade, whereby rotation of said propeller blade causes fluid to enter said opening, the fluid so entering then flowing through said conduit and escaping from said conduit through said slot thereby forming a curtain of fluid between the periphery of said blade and said housing.

References Cited in the file of this patent UNITED STATES PATENTS 2,156,133 Troller Apr. 25, 1939 2,597,510 McBride May 20, 1952 FOREIGN PATENTS 400,913 Great Britain of 1933 

1. AN ENCLOSED PROPELLER BLADE ASSEMBLY COMPRISING A BLADE MOUNTED TO ROTATE ABOUT AN AXIS, A HOUSING FOR SAID BLADE, SAID HOUSING BEING CIRCULAR IN SHAPE AND CONCENTRIC WITH THE CYLINDRICAL SURFACE DESCRIBED BY THE PERIPHERY OF SAID BLADE LEAVING A DETERMINATE CLEARANCE BETWEEN ITS INNER SURFACE AND SAID CYLINDRICAL SURFACE, THE SAID BLADE HAVING A PERIPHERAL PORTION AND A LEADING EDGE AND BEING PROVIDED WITH A CONDUIT CONFIGURED SUBSTANTIALLY SIMILAR TO AND LOCATED ADJACENT SAID PERIPHERAL PORTION, SAID CONDUIT INTERSECTING THE LEADING EDGE OF SAID BLADE AND HAVING AN OPENING FORMED AT SUCH INTERSECTION, AN ELONGATED SLOT LOCATED IN THE PERIPHERAL PORTION OF SAID BLADE AND BEING LONGITUDINALLY COTERMINOUS WITH SAID CONDUIT, SAID SLOT LONGITUDINALLY INTERSECTING BOTH THE CONDUIT AND THE PERIPHERY OF SAID BLADE, WHEREBY ROTATION OF SAID PROPELLER BLADE CAUSES FLUID TO ENTER SAID OPENING, THE FLUID SO ENTERING THEN FLOWING THROUGH SAID CONDUIT AND ESCAPING FROM SAID CONDUIT THROUGH SAID SLOT THEREBY FORMING A CURTAIN A FLUID BETWEEN THE PERIPHERY OF SAID BLADE AND SAID HOUSING. 